1. Field of the Invention
The present invention relates generally to the manufacture of nanocomposites comprising nano-sized materials and polymer resin, and more specifically to the manufacture of nanocomposites using monomer stabilization.
2. Description of Related Art
Vinyl ester resin has been widely used in the marine (Naval submarine) industry due to its good mechanical properties such as large Young's Modulus and tensile strength, and its superior resistance to moisture and chemicals. As a thermosetting material, vinyl ester resin can be cured easily in an ambient condition and was reported to strongly depend on curing temperature, initiators and accelerator levels. Separately, nano-sized materials are of tremendous interest in different fields of chemistry and physics due to their unique magnetic properties such as high coercivity and chemical catalytic properties inherent with their small size and high specific surface area.
Polymeric nanocomposites reinforced with nanoparticles have attracted much interest due to their cost-effective processability and tunable physical properties such as mechanical, magnetic, optical, electric and electronic properties. Inorganic nanofillers dispersed into polymer matrices can stiffen and strengthen the nanocomposites, increase the electric and thermal conductivities, introduce unique physicochemical properties such as magnetic and optical properties, and even improve the shape replicability. The use of proper functional nanoparticles within a polymeric matrix renders the resulting nanocomposites applicable in devices such as photovoltaic (solar) cells, polymer-electrolyte membrane fuel cells, and magnetic data storage systems. The functional groups of the polymer surrounding the nanoparticles enable these nanocomposites to be used for various industrial applications, such as site-specific molecule targeting applications in the biomedical areas and explosive detection sensors. Recent investigations on nanocomposites reinforced with different ceramic nanoparticles, such as alumina, zinc oxide, iron oxide and copper oxide, have shown that the ceramic nanoparticle itself has some effect on the curing process and subsequent performance of nanocomposites.
Nonetheless, industrial applications of bare vulnerable metal nanoparticles are still a challenge due to their aggregation and easy oxidation. To achieve a stable nanoparticle usable system in the context of nanocomposites, metal nanoparticles are usually stabilized by a surfactant/polymer or a noble metal shell, which reduces the particle agglomeration in a colloidal suspension or protects them from oxidation in harsh environments. High particle loading, required for certain applications such as solar cells, electromagnetic interfaces (EMI), microwave absorbers and giant magnetoresistance sensors, usually has a deleterious effect on the mechanical properties due to the particle agglomeration and poor interfacial bonding between the nanoparticle and polymer matrix. Therefore, particles are functionalized by a surfactant or a coupling agent to achieve uniform particle dispersion in the matrix and chemical bonding at the interface. There still lacks a systematic study of the nanoparticle effect on the curing process for high-quality vinyl ester resin nanocomposite fabrication, especially for the case of reactive magnetic metallic nanoparticles. In addition, the functionalization of nanoparticles made the composite fabrication more complicated and costly.
Metallic multilayer giant magnetoresistance sensors (GMRs) have found wide applications in areas such as biological detection, magnetic recording and storage systems, and rotational sensors in automotive systems since the discovery of GMR in 1988. Compared with the metal-based multilayer GMR sensors, the polymer nanocomposite-based sensors would have the benefit of easy manipulation and cost-effective fabrication. However, the challenge is to obtain high-quality polymer nanocomposites with nanoparticles uniformly dispersed in the polymer matrix. In other words, to prevent particle agglomeration is an inherent challenge in the composite fabrication. In addition, the interaction between the nanoparticles and the polymer matrix plays an important role in the quality of the nanocomposite. Poor linkage, such as the presence of gas voids may result in deleterious effects on the mechanical properties of the nanocomposites.